The present invention relates to a valve, and in particular, though not limited to a flow control valve which is particularly suitable for controlling the flow of fuel gas to a gas powered appliance. The invention also relates to a gas burner, and to a gas burner incorporating the valve.
Flow control valves which are typically used for controlling the supply of fuel gas to a gas powered appliance, for example, a gas powered heater, a gas powered oven, a gas powered hob or the like, may be manually operated or may be motor operated by, for example, a servo-motor, and in some cases may be operated by a solenoid coil. Typically such valves comprise a valve housing which define a hollow interior valve chamber. An inlet port is provided to the valve chamber, while an outlet port is provided from the valve chamber. A valve seat is formed within the valve chamber between the inlet and the outlet ports, and defines a fluid passageway between the respective inlet and outlet ports. A valving member located within the valve chamber co-operates with the valve seat for closing the communicating passageway for in turn closing the valve. In a manually operated valve the valving member is manually urged into and out of engagement with the valve seat by a manually operable mechanism connected to the valving member for closing and opening the fluid passageway. In the case of motor or solenoid operated valves the valving member is urged into and out of engagement with the valve seat by a servo-motor or a solenoid. An urging means, typically, a compression spring is provided for urging the valving member into engagement with the valve seat in the event of an emergency, and it is necessary to isolate the appliance from the gas supply. Various arrangements are provided for disengaging the valving member from the manual drive mechanism, the servo-motor or the solenoid in order that the valving member can be urged by the compression spring into engagement with the valve seat independently of the various drive mechanisms. However, in general, such arrangements for disengaging the valving member from the drive mechanism suffer from a number of disadvantages. Firstly, in many cases they are slow to react, and secondly, in general, it is difficult if not impossible to establish the absolute position of the valving member relative to the valve seat. This is a serious disadvantage, since it prevents accurate and precise control of the flow of fuel gas through the valve, and in general, setting of the flow of fuel gas through the valve to a desired flow rate can only be achieved by trial and error.
There is therefore a need for a valve which permits the absolute position of a valving member in a valve to be established, whether the valving member is disengageable from a drive means for operating the valving member or not, and additionally, there is a need for a gas burner, and a gas burner incorporating such a valve.